1. Field of the Invention
The present invention relates to an improvement on the transmission mechanism of a carving grinder, especially to a transmission mechanism of a carving grinder capable of maintaining concentricity when rotating and increasing the stability to reduce run-out in transmission.
2. Description of the Prior Art
A carving grinder seeks primarily to maintain the stability of the machine when rotating, because a perfect and delicate work cannot be achieved without stability of the tool. Accordingly, development and improvement has been going on in the industry. In prior art of carving grinder, US Application No. 2008/0176493A1, for example, disclosed an improved grinding assembly (hereinafter called the “Citation”), which comprises: a motor, a transmission pipe and a handle, wherein the motor can be hung, and the transmission pipe includes a soft hose and a guide pipe which is received in the soft hose, one end of the transmission pipe connected to the motor and the other end connected to a male connector; fitted in the male connector is a bearing; the guide pipe consists of a spiral pipe and a steel cable which extending through the spiral pipe, a distal end of the steel cable connected to a driving member which extends through said bearing and the male connector by an appropriate length; whereby the driving member extends suspended between the bearing and an axle in the handle to avoid the contact of the driving member with the inner periphery of the male connector when the tool is in use. While aiming to increase precision in product by such arrangement, the Citation still has the following drawbacks: using just one bearing is not good enough to reduce the friction between the driving member and the male connector, and the magnitude of vibration due to the driving member run-out when the driving member itself is driven by motor is not dealt with, as only one bearing is provided on the driving member to reduce the friction, despite that the greatest power comes from the motor. Hence the stability of a tool according to Citation has yet to be improved.
Also, in prior art of grinding assembly, the embossed key 61 of transmission axle 60 is made by secondary pressing work (as FIG. 1 shows); as a result, concentricity tends to decrease to an extent that there may be deviation when the axle rotates at high speed. That compromises the precision for the work, which is also an issue the industry has tried hard to tackle.
Furthermore, in prior art, the coupling of the transmission tube 70 and the male connector 71 is joining of a passage 72 and a round hole 73, as FIG. 2 shows, which tends to become loose in fitting from high-speed rotation, which in turn affects the stability of the rotation.
It is thus clear that in prior arts, the problem of run-out in transmission was not much improved, and the drawbacks like compromised concentricity affected the precision and quality.